Mutual Soluhility of Liquids. 645 



(fig. 4), or by a separation of the liquid-curve from the 

 vapour-liquid curve ou the outside (fig. 5). In the former 



Fiir. 4. 



Fin. 5. 



ic axis 



case the two branches of the liquid-curve converge towards 

 each other on the side of the ^ axis and meet in a critical 

 point C, w^hich disappears into the vapour-liquid curve at 

 the critical mixing temperature of the liquid layers, and 

 before this temperature is reached pressure will obviously 

 make the liquids a])proach the critical point and ultimatelj 

 mix. In the latter case the branches of the liquid- curve 

 diverge, at least to begin wnth, and the curve need not be 

 closed or have a critical point towards the small volumes ; but 

 at the moment when it separates from the main curve a 

 critical ])oint C, which was before hidden inside the vapour- 

 liquid curve, makes its appearance ; this critical point is thus 

 turned towards the vapour-liquid curve, i. e. it lies on the 

 side of the large volumes. Above the critical temperature, 

 after the two curves have separated, pressure will drive the 

 mixture into the liquid-curve, ?'. e. bring back the two layers. 

 Now^ phenol and water, as shown by van der Lee *, belong 

 to the latter type, but propane and methyl-alcohol were found 

 to conform to the former. The effect of pressure on the 

 critical point of the liquid phases below 21°- 15 is shown in 

 the following Table III. The pressure considered as a 

 function of the temperature rises much more slowly at first 

 than later. 



* Van der LcC; DtsscrtnfwVy aud Zeitsch, Phjjsik. C/ienu'e, xxxiii. 

 p. Hl>0. 



